2001 Town Country A/C Problem

I have a 2001 T&C LXI. In the early summer, I began smelling a musty odor when the AC turned on. Soon after, my AC began blowing hot air. I brought it to a mechanic. He added freon and a dye to see where the leak could be. He could not find one - I told him about the musty odor and he said that he has had many Chrysler/Dodge/Plymouth minivans in with the same problem. He said that it the evaporator leaks behind the dash and that it is approx. $800 to repair.

Has anyone else had this problem - OR - have any input into this problem?

We had this problem also (with A/C on). They told us the cost was because they had to take the dash apart. WhatEVER!
Winter is almost here..........no more A/C.